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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

COTTONSEED OIL

401

2. Detection of Adulterations.—Colza and ravison oils may be found
mixed with olive oil (q.v.) and, in their turn, may be adulteratedVith other
seed oils (linseed, poppyseed, cameline, hempseed, etc.), and particularly
with fish oils and oils of other marine animals, as well as with mineral oils

The determination of the various characters (especially saponification,
iodine and Maumene numbers) and the test for erucic acid by Tortelli and
Fortini's method readily show if the oil is pure or otherwise. Seed oils in
general and animal oils raise the saponification number, while linseed, hemp-
seed and poppyseed oils raise also the iodine and Maumene numbers. Fish
oils and other marine animal oils are detected by means of the cest for the
octabromo-compounds and the Tortelli and Jaffe reaction (see Fish Oils),
and mineral oils by testing for unsaponifiable substances.

***

Colza oil for comestible and illuminating purposes should be well refined and
not acid. Industrial ravison oil should have : D =0-911-0-937, iodine number
= 103-108, saponification number = 175-178, refractive index (Zeiss) at 25°
= 68-71, Maumene number (Tortelli) =60-8°.

COTTONSEED OIL

Obtained from the seeds of Gossypium herbaceum. It is yellow or golden-
yellow or, if not well refined, slightly reddish-yellow ; it has characteristic
but not very pronounced smell and taste. About 18 grams dissolve in
1000 c.c. of absolute alcohol at 15°. The other physical and chemical
characters are indicated in Table XLIV.

Heydenreich's reagent gives a deep orange, and Hauchecorne's or Brulle's
reagent a reddish-brown, coloration with the oil. The latter also gives
the following characteristic reactions :

1. Milliau's Reaction, modified by Armani.—10 grams of the oil
are saponified in the usual way, the soap being dissolved in water and the
solution shaken in a separating funnel with 100 c.c. of ether and 30 c.c.
of 10% hydrochloric acid. After standing, the acid aqueous layer is removed
and the ethereal solution of the fatty acids washed by shaking several times
with water until the latter no longer gives an acid reaction. The ether is
then evaporated, the fatty acids thus obtained being dissolved in 15 c.c.
of 90% alcohol (puriss.) 1 and the solution mixed with 1-2 c.c. of alcoholic
silver nitrate solution and heated in a water-bath at 80-90°.

Pure cottonseed oil gives an intense brown coloration almost immediately
and then also a black precipitate. Mixtures of oils or fats containing cotton-
seed oil yield a violet-brown coloration which, after a few minutes' heating,

1 This reaction and in general all reactions with silver nitrate require the use of
very pure alcohol, which does not show the least brown coloration on protracted heating
with silver nitrate. The absolute alcohol of commerce may be purified as follows
(Tortelli and Ruggeri): A litre of alcohol is heated for an hour in a reflux apparatus
with 3 c.c. of 5;% silver nitrate solution and then distilled. The distillate is treated
with potassium permanganate until it assumes a persistent red colour and is then left
for 24 hours with occasional shaking and subsequently filtered. The filtrate is treated
with 2 grams of pure caustic potash, heated for an hour in a reflux apparatus and
distilled, the distillate being diluted to the desired strength with distilled water.
A,C,                                                                                                    26683), an4 Evers (Analyst,